Xylose and cellobiose fermentation to ethanol by the thermotolerant methylotrophic yeast

Ryabova, Olena B.; Chmil, Oksana M; Sibirny, Andriy А.

doi:10.1016/s1567-1356(03)00146-6

Cited by 145 publications

(96 citation statements)

References 29 publications

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“…subjected to different pretreatments contain different (and variable) concentrations of different sugars. In regard to the desired end products of depolymerization, wild-type Saccharomyces cerevisiae (yeast) can ferment glucose but not xylose, whereas xylose and cellooligosaccharides are acceptable to other native or engineered microbes [28,51]. Therefore, biomass source, pretreatment, enzyme mixture, and fermentation microbe are interdependent variables.…”

Section: Enzymes For Biomass Conversionmentioning

confidence: 99%

Improving Enzymes for Biomass Conversion: A Basic Research Perspective

2010

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The cost of enzymes for converting plant biomass materials to fermentable sugars is a major impediment to the development of a practical lignocellulosic ethanol industry. Research on enzyme optimization with the goal of reducing the cost of converting biomass materials such as corn stover into glucose, xylose, and other sugars is being actively pursued in private industry, academia, and government laboratories. Under the auspices of the Department of Energy Great Lakes Bioenergy Research Center, we are taking several approaches to address this problem, including "bioprospecting" for superior key enzymes, protein engineering, and high-level expression in plants. A particular focus is the development of synthetic enzyme mixtures, in order to learn which of the hundreds of known enzymes are important and in what ratios. A core set comprises cellobiohydrolase, endoglucanase, β-glucosidase, endoxylanase, and β-glucosidase. Accessory enzymes include esterases, proteases, nonhydrolytic proteins, and glycosyl hydrolases that cleave the less frequent chemical linkages found in plant cell walls.

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Section: Enzymes For Biomass Conversionmentioning

confidence: 99%

Improving Enzymes for Biomass Conversion: A Basic Research Perspective

2010

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“…Other researchers used different types of microorganisms at different conditions to produce ethanol, e.g., wild-type strains of yeast Hansenulapolymorpha to ferment glucose, cellobiose and xylose to ethanol [14]; bioethanol production from DOI: 10.7763/IJCEA.2013.V4.280 bioethanol is produced in America [3], [4] (see Table I). …”

Section: Introductionmentioning

confidence: 99%

Production of Bioethanol Fuel from Low-Grade-Date Extract

Sulieman¹,

Gaily²,

Zeinelabdeen³

et al. 2013

IJCEA

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Abstract-Experiments on production of bioethanol through anaerobic fermentation of sugars extracted from low-quality dates using a wild strain of Saccharomyces cerevisiae were conducted at 30C and 33C. The effect of the pH during fermentation was insignificant at the operating temperatures.The average ethanol yield for all experiments was greater than 71% of its theoretical value. Experiments in a 1L volume fermentor at 30C and 120 rpm without controlling the pH during fermentation gave ethanol yields of 91.3%, 68.7% and 54.8 % for the 10, 15 and 20% initial sugar concentrations, respectively. The drop in ethanol yield for 20% sugars could be attributed to probable ethanol inhibition.

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“…Also, H. polymropha is a biotechnologically important yeast known as an efficient expression platform for heterologous proteins, governed mostly by glucose-repressible promoters (14,21). In addition, this thermotolerant yeast has recently been suggested as a promising organism for hightemperature fermentation of major sugars of lignocellulose hydrolysates, glucose and xylose (38). Therefore, comprehensive knowledge of the glucose-triggered pathways in this yeast is required to optimize the H. polymorpha expression platform or to construct strains capable of simultaneous utilization of glucose and other sugars derived from lignocellulose.…”

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Identification of Hexose Transporter-Like Sensor HXS1 and Functional Hexose Transporter HXT1 in the Methylotrophic Yeast Hansenula polymorpha

et al. 2008

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We identified in the methylotrophic yeast Hansenula polymorpha (syn. Pichia angusta) a novel hexose transporter homologue gene, HXS1 (hexose sensor), involved in transcriptional regulation in response to hexoses, and a regular hexose carrier gene, HXT1 (hexose transporter). The Hxs1 protein exhibits the highest degree of primary sequence similarity to the Saccharomyces cerevisiae transporter-like glucose sensors, Snf3 and Rgt2. When heterologously overexpressed in an S. cerevisiae hexose transporter-less mutant, Hxt1, but not Hxs1, restores growth on glucose or fructose, suggesting that Hxs1 is nonfunctional as a carrier. In its native host, HXS1 is expressed at moderately low level and is required for glucose induction of the H. polymorpha functional low-affinity glucose transporter Hxt1. Similarly to other yeast sensors, one conserved amino acid substitution in the Hxs1 sequence (R203K) converts the protein into a constitutively signaling form and the C-terminal region of Hxs1 is essential for its function in hexose sensing. Hxs1 is not required for glucose repression or catabolite inactivation that involves autophagic degradation of peroxisomes. However, HXS1 deficiency leads to significantly impaired transient transcriptional repression in response to fructose, probably due to the stronger defect in transport of this hexose in the hxs1⌬ deletion strain. Our combined results suggest that in the Crabtree-negative yeast H. polymorpha, the single transporter-like sensor Hxs1 mediates signaling in the hexose induction pathway, whereas the rate of hexose uptake affects the strength of catabolite repression.As a favorite carbon substrate, glucose exerts numerous strong and well-coordinated effects on the physiological state of yeast cells. They include gene-specific regulation of transcription and mRNA stability as well as regulation at the posttranslational level: e.g., catabolite inactivation of certain glucoserepressible enzymes (3,13,19). Signaling pathways involved in different glucose effects have been studied mostly in the model yeast Saccharomyces cerevisiae. A number of participating components have been identified, and some have been shown to have conserved functions in other yeast species (for review, see references 12, 36, and 41). Nevertheless, knowledge of glucose-triggered regulatory pathways for Crabtree-negative yeasts (which contrary to S. cerevisiae, are unable to produce ethanol aerobically in the presence of high external glucose concentrations) (11) that primarily rely on respiratory metabolism still remains very limited. In particular, the first stages, how glucose is sensed, and the molecular triggers involved in different pathways are the least understood aspects of these yeast species.Two nontransporting glucose carrier homologues, Snf3 and Rgt2, have been shown to function as glucose sensors in S. cerevisiae in a pathway of transcriptional induction. They differentially regulate expression of the functional hexose transporters in response to extracellular glucose concentration (32). This ...

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Xylose and cellobiose fermentation to ethanol by the thermotolerant methylotrophic yeast

Cited by 145 publications

References 29 publications

Improving Enzymes for Biomass Conversion: A Basic Research Perspective

Improving Enzymes for Biomass Conversion: A Basic Research Perspective

Production of Bioethanol Fuel from Low-Grade-Date Extract

Identification of Hexose Transporter-Like Sensor HXS1 and Functional Hexose Transporter HXT1 in the Methylotrophic Yeast Hansenula polymorpha

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